The ornamental design for a light mount, as shown and described.
FIG. 1 is a perspective view of a light mount;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a left side view thereof; and,
FIG. 7 is a right side view thereof.
The dash-dot broken line immediately adjacent to the shaded areas discloses the boundary of the claim; the evenly broken line discloses unclaimed portion of the light mount; the broken lines form no part of the claimed design.